email adress is not supported

When I want to sync my account, an error sign pops up telling me “This Email adress is not supported”. The error occured shortly after I registered a new email account within the eM client program, however, I was able to synchronize my mails at least one time. 

Can you post more of the error, which you can find in Menu > Tools > Operations.

This is what pops up:

19:49:23   System.FormatException: Unsupported mail address

19:49:23    at MailClient.Mail.MailAddress.Create(String encoded)

19:49:23    at MailClient.Mail.MailAddress.Create(String displayName, String encodedAddress)

19:49:23    at MailClient.Protocols.Exchange.ExchangeToMimeConverter.ConvertEmailAddress(EmailAddress address)

19:49:23    at MailClient.Protocols.Exchange.ExchangeToMimeConverter.<>c.b__11_0(EmailAddress
a)

19:49:23    at System.Linq.Enumerable.<>c__DisplayClass13_0`2.b__0(TSource
item, Int32 i)

19:49:23    at System.Linq.Enumerable.d__15`2.MoveNext()

19:49:23    at System.Collections.Generic.List1..ctor(IEnumerable1 collection)

19:49:23    at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)

19:49:23    at MailClient.Protocols.Exchange.ExchangeToMimeConverter.ConvertEmailAddresses(EmailAddressCollection addresses)

19:49:23    at MailClient.Protocols.Exchange.ExchangeToMimeConverter.CreateEnvelope(EmailMessage message)

19:49:23    at MailClient.Protocols.Exchange.ExchangeMailSynchronizer.d__12.MoveNext()

19:49:23    at System.Collections.Generic.List1.InsertRange(Int32 index, IEnumerable1 collection)

19:49:23    at MailClient.Protocols.Exchange.ExchangeItemSynchronizer`2.ConvertApplicationDataAndSkipUnparsable(ExchangeService service, Item item, CancellationToken cancellationToken)

19:49:23    at MailClient.Protocols.Exchange.ExchangeItemSynchronizer`2.d__18.MoveNext()

19:49:23    at System.Linq.Enumerable.d__20`3.MoveNext()

19:49:23    at System.Linq.Enumerable.d__15`2.MoveNext()

19:49:23    at MailClient.Protocols.Common.ItemSynchronizeContext2.StoreItems(SynchronizationType synchronizationType, IEnumerable1 newItems)

19:49:23    at MailClient.Protocols.Common.MailItemSynchronizeContext.StoreItems(SynchronizationType synchronizationType, IEnumerable`1 newItems)

19:49:23    at MailClient.Protocols.Common.ItemSynchronizeContext2.Synchronize[T](SynchronizationType synchronizationType, IEnumerable1 items, Func2 getUniqueId, Func3 hasChanged, Func2 isDeleted, Func2 convertItems, Action`2 updateItem)

19:49:23    at MailClient.Protocols.Exchange.ExchangeItemSynchronizer2.Synchronize(IItemSynchronizeContext1 synchronizeContext, Folder folder, CancellationToken cancellationToken)

19:49:23    at MailClient.Protocols.Common.ItemSynchronizer`2.<>c__DisplayClass32_0.b__1(WorkerStatus
status, CancellationToken cancellationToken)

19:49:23    at MailClient.Protocols.Exchange.ExchangeGenericCommand.Execute(WorkerStatus status)

19:49:23    at MailClient.Commands.Command.Process(WorkerStatus status)

What happens if you remove that account from eM Client, then add it again?